nios2: change virt_to_phys to use physaddr_mask in global data

As virt_to_phys() is used a lot in DMA transfer, change it
to use physaddr_mask in global data. This will save an "if"
statement and get a little faster.

Signed-off-by: Thomas Chou <thomas@wytron.com.tw>
Acked-by: Marek Vasut <marex@denx.de>
diff --git a/arch/nios2/include/asm/io.h b/arch/nios2/include/asm/io.h
index e04050f..03a3418 100644
--- a/arch/nios2/include/asm/io.h
+++ b/arch/nios2/include/asm/io.h
@@ -44,10 +44,7 @@
 static inline phys_addr_t virt_to_phys(void * vaddr)
 {
 	DECLARE_GLOBAL_DATA_PTR;
-	if (gd->arch.has_mmu)
-		return (phys_addr_t)vaddr & 0x1fffffff;
-	else
-		return (phys_addr_t)vaddr & 0x7fffffff;
+	return (phys_addr_t)vaddr & gd->arch.physaddr_mask;
 }
 
 static inline void *ioremap(unsigned long physaddr, unsigned long size)